Need Suggestion for following sceneario

I need suggestion for the following scenario
1) There are X number of word Documents saved in a hard disk
2) In Web application upon some action
2.1) the logged in user details has to be fetched from database
2.2) the User details(userId,UserName,Desigantion (hardly some 9 informations)) has to be filled in one of the documents, which has been mentioned in the Step 1.
3) Generate the PDF with the modified content and send it to browser for download.

Solutions
1) Load All the documents into memory as a String or StringBuffer format while application server start up & replace(fill userid, userName and some information) the String or String Buffer & Generate the PDF
2) Load only the requested or specific document as a String or StringBuffer format & replace the String or String Buffer & Generate the PDF
3) Take the contents of word as constants of String Objects and create java program for generating the PDF.

I Think the first two approach will give OutOfMemoryException if everything gets loaded into memory, The Third approach will be performance impact because of more String operations.